/Engine/Plugins/FX/Niagara/Source/Niagara/Classes/NiagaraDataInterfaceAudio.h
Copies the minimum of NumSamples or however many samples are available into OutBuffer. Returns the number of samples copied, or -1 if this output's corresponding input has been destroyed.
int32 PopAudio ( float * OutBuffer, int32 NumSamples, bool bUseLatestAudio )